1. Field of the Invention
It is well recognized in the field of Urology that persons lose control of their urinary function. This loss of control may be temporary or permanent, depending upon the cause of the loss of urinary function. Temporary loss may be caused by a disease entity which is curable by medical or surgical treatment, whereas permanent loss of control may be caused by an incurable disease entity or physical trauma resulting in partial or total paralysis of the muscles which cause normal urination. The bladder is a dome shaped container with muscular walls and which accepts urine from the kidneys for temporary storage. During normal voluntary urination, the muscles in the bladder wall contract and simultaneously the sphincter muscle surrounding the opening in the bladder which communicates with the urethra relaxes so that the urine stored in the bladder is released into the urethra and expelled from the body.
The causes for loss of normal voluntary control of the urination process are manifold and the consequences are indeed severe. If urine cannot be periodically expelled from the bladder, the urine becomes stagnant and bacteria multiply at an exceedingly rapid rate, resulting in infection of the bladder. Chemical changes in the urine due to the infection cause painful urination and can also cause general dibilitation of health. If, after infection occurs, the urine retention is still permitted to continue for any considerable length of time beyond normal voluntary urination frequency, ascending infection can occur, that is the infection in the bladder spreads to the ureters and to the kidneys, thereby causing still more serious consequences, such as failure of one or both of the kidneys to function. If the kidneys do not function to cleanse the blood of impurities and form urine, uremia results and death occurs in the absence of the availability of recently developed artificial kidney machines. If, on the other hand, the kidneys continue to function and fill the non-draining bladder with urine, the bladder can burst, thereby emptying the bacteria laden urine into the abdominal cavity. The usual result of this is peritonitis, which is an inflammation of the peritoneum, the membrane that lines the abdominal cavity, and the results of inflammation of this membrane are always serious. The time between the occurrence of acute peritonitis and death may be only a matter of a few hours to a few days depending upon the severity of the infection. Septicemia, an infection of the blood, is another serious consequence of excessive retention of urine in the bladder, since the bacteria in the bladder, ureters and kidneys invades the blood through the minute blood capillaries in these organs.
Obviously other complications, bodily disorders and disfunctions and serious consequences, too numerous to mention herein, can result from failure of proper urination. It is obvious that constant periodic drainage of the bladder to eliminate urine and other body waste material is essential not only to good health but to maintaining life itself.
Techniques of treatment for loss of normal voluntary control of the urination process are relatively few in number. Depending on the nature of the cause, a super-pubic technique involving surgery may eliminate the drainage problem in some circumstances. Since surgery is involved, this treatment is traumatic and severe, and is utilized only when absolutely necessary. Drug therapy is effective in some cases to promote drainage of the bladder, but due to the relatively few causes of loss of voluntary control which will respond to drugs and the ever presence of undesirable side effects, drug therapy is considered to be a relatively ineffective method of dealing with the problem.
2. Necessity for Practice of Invention
Since the loss of voluntary control over the urinary function is typically a secondary effect caused either by disease or trauma, it has become a well established medical practice to relieve the urinary drainage problem mechanically by means of the process of catheterization. If the primary cause of the loss of voluntary urination control is from a curable disease, the catheterization process is maintained on a temporary basis only for so long as necessary until voluntary control returns. If the cause of loss of control is permanent, as in the case of paralysis such as with paraplegics and quadriplegics, the catheterization process must be maintained on a permanent basis in order to maintain life.
In the catheterization process, a tube or catheter is inserted into and through the urethra until the remote or distal end is located within the bladder, usually being disposed just past the sphincter muscle at the juncture of the bladder with the urethra. The near or proximal end of the tube remains outside of the body and there is thus provided a path or channel through which urine in the bladder can drain as the need arises. Once a catheter has been passed through the urethra and inserted into the bladder, it is generally necessary, in connection with the disease and trauma conditions described above, to have the catheter retained in the urinary tract with the distal end of the catheter in the bladder, such retention being in the order of several days to several weeks without removal. Catheters which are designed for use a function are called urinary retention catheters and are typically provided by including an inflatable balloon at the distal end of the catheter which is deflated during insertion of the catheter and which is inflated by passing a fluid, typically water or saline solution through a passage within the catheter, called an inflation lumen. Thereafter, fluid from the bladder drains through the main passage of the catheter, called the drainage lumen.
3. Problems of Catheterization
Inserting a catheter into the urethra can be a painful and traumatic experience, the degree of pain and trauma depending on the construction of the catheter being inserted, the technique for inserting it, and the experience and the skill of the person performing the insertion whether that person is the doctor or other individual. Since the designers of catheters have no control over the last named characteristic, the present invention has been developed with the first two characteristics principally in mind, but also with consideration for the fact that the catheter may on many occasions be inserted by other individuals who would not be as skilled as the doctor. The reason for possible pain and trauma is that the urethra, whether male or female, is a relatively tortuous tube of varying cross-sectional dimensions and is normally collapsed along most of its length. The upper portion of the urethra is provided with sphincters or valves which it enters the bladder neck. The female urethra is somewhat shorter and straighter than the male urethra but otherwise both are much the same. The urethra is a very delicate organ and cannot withstand any appreciable amount of lateral pressure against the urethral wall without causing some degree of rupture. Since the urethra has a high concentration of pain sensing nerve endings, any distortion, whether of change in size or shape, is very uncomfortable at the least and usually painful, and any trauma to the urethra is accompanied by a great deal of pain. It is not uncommon for the patient to have to be anesthetized in order to insert many common urinary catheters. In addition to the pain, bacteria in the urethra can enter the blood stream if the urethra is traumatized, with the same result discussed above in connection with rupture of the bladder.
Extensive research and development have been carried out over a long period of time in the design of catheters, and a large number of different catheter designs appear in the medical and patent literature. The reason for this is that design characteristics for urinary drainage catheters are highly conflicting from the standpoints of patient discomfort and functionalism. In order to reduce the probability of trauma and resulting pain to the urethra as well as discomfort to the patient during long periods of retention, a urinary drainage catheter should be as thin as possible, highly flexible and pliant, and have a soft rounded end. From the functional standpoint, on the other hand, the catheter must be of sufficiently thick and rigid construction that it will not buckle while being passed through the urethra, it should have as wide a drainage opening and lumen as possible to promote complete drainage and prevent clogging, and the end should be free and unobstructed in order to facilitate the use of the catheter as an aid to the insertion of diagnostic and treatment instrumentation into the bladder. Of great importance is the fact that a retention catheter must have an effective means for retaining the catheter in place in the bladder which will not obstruct either the flow of urine or substantially the complete drainage of urine therefrom, but at the same time has sufficient retaining capability that a patient, particularly a senile patient, cannot forcibly pull the catheter out of the bladder and into the urethra thereby causing extreme damage thereto. Further, any urinary drainage catheter must be formed of a material totally inert to the effects of urine and other waste materials, be capable of absolute sterilization, and be manufacturable to strict tolerances, in high volume and at low cost considering the disposable nature of the product. Still other criteria may be apparent to those skilled in the art.
4. The Prior Art
In view of the foregoing diverse criteria, the basic design of commercially available retention catheters has changed very little over the past half century, and the well known Foley retention catheter is almost universally used by doctors, hospitals, nursing homes, etc. to alleviate loss of voluntary bladder control U.S. Pat. Nos. 2,892,458; 2,936,761; 3,292,627 and 3,394,705 are mentioned as illustrating typical prior art catheters which are usually formed of relatively thick walled construction so as to be insertable without buckling, have a rounded solid tip to prevent trauma to the delicate lining of the urethra, and have side openings adjacent the tip to communicate the interior of the bladder with the drainage lumen. The prior art catheters also have an inflatable balloon portion beyond the drainage opening in order to retain the catheter in place. These catheters, and many more like them, are undesirable from the standpoint that considerable pain may be experienced in introducing a relatively wide, semi-rigid catheter into a relatively narrow urethra. Further, the small side openings can easily clog from clots of sediment material which collects in the bottom of the bladder. Still further, as a result of the solid tip, it is impossible to pass diagnostic or treatment instrumentation through the catheter for the purpose of inspecting or treating the interior of the bladder. The capability of inserting instrumentation through the catheter after it is in place is very important in the urological practice since prior treatment involves the use of anesthesia in order to insert steel tube instrumentation as has been the practice.
In U.S. Pat. No. 2,677,375, recognition was given to the desirability of removing the fixed rounded tip so as to provide a drainage opening adjacent the inflatable retention balloon. Strips are provided across the opening for engagement by an inserting stylet. This construction is disadvantageous in that the strips are likely to obstruct the passage of sediment clots and thus clog the drainage opening, and even more harmful is the fact that the insertion of such a blunt end as is apparent in this device is almost certain to cause considerable trauma to the delicate wall of the urethra. It is also apparent that it would be at least difficult, if not impossible, to pass instrumentation through this catheter in view of the strips across the open end. Such a device would be wholly unacceptable to the urological practitioner.
A significant aspect of the present invention is the provision of an improved stylet which is utilized both during insertion of the catheter through the urethral passage and thereafter as a cleaning implement. U.S. Pat. Nos. 2,118,631; 2,164,926 and 2,856,934 are cited as representative of prior art stylets which are utilized solely to assist in inserting the catheter, the first two being of the typical push rod type and the third being of the filiform type. Although the use of a stylet to insert the catheter obviates the problem of bucking of the catheter during insertion and thereby permits the catheter to have a relatively thin wall construction, the push rod type used in conjunction with a closed end catheter is undesirable from the standpoint that there is no way of accurately ascertaining when the end of the catheter enters the bladder because the stylet blocks the drainage opening or the drainage lumen or both. The filiform device is undesirable because of the possibility of injuring the delicate wall of the urethral passage during the insertion of the filiform unless great care is exercised because of the fact that the filiform is of necessity very thin and therefore must be relatively rigid and sharp nosed. Other disadvantages of this technique for inserting drainage catheters will be apparent to those skilled in the art.
Another significant improvement of the present invention is the novel construction of the inflatable retention balloon to cause the open end of the catheter to expand and widen, which assists in drainage and in retention. Some consideration has been given to this problem as evidenced by U.S. Pat. No. 2,892,458 mentioned above, as well as by U.S. Pat. Nos. 3,438,375 and 3,889,686. In the first patent, the balloon is constructed to be less inflatable adjacent the lateral drainage opening through the catheter wall so that the balloon cannot overlie and block the opening if the catheter tends to settle in the bladder or is pulled by the patient. In U.S. Pat. No. 3,438,375, the opposite theory is applied and the balloon is constructed to purposely overlie the lateral drainage but be spaced therefrom so that the delicate lining of the bladder cannot be drawn into the opening by sub-atmospheric pressure. In U.S. Pat. No. 3,889,686, a lateral opening is provided below the balloon as well as above so as to promote better drainage. All of these techniques have inherent disadvantages in that they present design problems which are difficult to overcome in manufacturing the catheter, they are not nearly as effective in practice as eliminating the lateral drainage opening altogether so that the inflation balloon presents no interference problem whatever, and they cannot function to allow movement of a stylet to indicate when the balloon is inflated because the rounded tip closes the longitudinal end of the drainage lumen.